1. Field of the Invention
The invention relates to the art of continuously forming packages from flexible sheet material.
2. Prior Art
The art of continuously forming packages from flexible sheet material includes methods and apparatus in the following general catagories: (1) wraps, (2) preformed bags, and (3) form/fill/seal pouches. In all of the above categories, the packages are formed from flexible sheet materials, such as, for example; paper, cellophane, plastic films, aluminum foil, or a combination of the above. It will be appreciated that such packages have the inherent characteristics of being light in weight; space saving; relatively low cost; adaptable to various production, distribution, and retailing techniques; and functional for various end uses and ultimate disposal.
Wraps and preformed bags are considered to be the traditional packaging methods in the present packaging industry. Wrapping involves the utilization of a sheet of flexible material such as paper, cellophane, film, foil, or a laminated film. Generally, the sheet is fed from a supply roll and folded around the product to be packaged. Traditionally, wraps have been developed for specific products in conjunction with specific types of equipment and systems. Examples of products which have been packaged with the above method include bread, candy and cigarettes.
Preformed bags are also an old and well known form of packaging which were originally made by hand to provide convenience in handling, filling, and closing. The materials used for preformed bags include paper, cellophane, polyethylene, foil, and laminates of these materials. The introduction of plastic materials to this art has assisted in sustaining its popularity because of the advances made in the technology and graphics, especially the transparency enclosing systems which may be utilized. Products such as flour, sugar, and produce have bene typically packaged with this method.
The form/fill/seal pouch type of flexible packaging is considered to be an extension of the preformed bag art. The significant difference over the preformed bag is that the form/fill/seal pouch structure may be continuously formed from supply of web material which can be filled and heat-sealed by high-speed automated machines. Thus, a single machine may readily comprise an entire and complete packaging line.
There are basically three methods employed in the form/fill/seal packaging technique. Initially, the horizontal forming method includes a horizontally fed pouch which is produced in sequential steps, leaving the top seal opened for filling with the desired product, and final sealing. Generally, this involves a rather cumbersome mechanical process resulting in rather slow production rates.
The vertical forming method utilizes a vertically fed single web formed into a tube around a mandrel wherein the abutting seam is effectively sealed. The vertically disposed pouch is filled with the desired product, and then the top is sealed at the same time as the bottom of the next adjacent pouch is formed by sealing. Typically, the vertically fed pouch has enjoyed a considerable amount of popularity and acceptance because the technology inherently took advantage of the forces of gravity as an integral part of the packaging technique.
The third type of form/fill/seal pouch technology employing the rotary method of packaging seems to incorporate the advantages of the other above-discussed techniques while obtaining other advantages. Among some of the advantages are increased production speeds, eliminating impurity migration in the final seal, and proper registration of the filled pouches during production and thereby improving subsequent handling and treating operation. The other types of packaging techniques mentioned above have been plagued with migratory seals thereby, in an attempt to overcome the problems, the packaging machines were forced to operate at production speeds well below the designed capability. Even at the lower production speeds, the migratory seals resulted causing a premature spoilage in the packaged product and destroyed the aseptic potential of the process.